Equipment and process for creating a custom sloped etch in a substrate

ABSTRACT

Equipment and processes for creating a custom sloped etch in a substrate are disclosed. An illustrative process may include the steps of providing a substrate having a surface to be etched, providing a control layer on the surface of the substrate, forming a mask above the control layer, and then selectively etching each of the control layer and substrate at variable rates to form a sloped etch in the substrate.

FIELD OF THE INVENTION

The present invention relates generally to the field of semiconductormanufacturing and microelectromechanical systems (MEMS). Morespecifically, the present invention pertains to equipment and processesfor creating a custom sloped etch in a substrate.

BACKGROUND OF THE INVENTION

The creation of custom sloped etches is important in the manufacture ofmicroelectromechanical system (MEMS) devices and other small-scaledevices. In the construction of MEMS devices, for example, such customsloped etches can be useful in helping to reduce the voltage necessaryto electrostatically actuate small structures such as beams ordiaphragms, or to perform some other desired function. A sloped surfacemay, for example, allow an electrode that is positioned on the slopedsurface to be near one or more electrodes on a beam or diaphragm at onelocation. The electrode on the sloped surface may then slope away fromthe beam or diaphragm. This may allow the beam or diaphragm to beinitially actuated with a relatively small voltage, and then roll downalong the sloped surface to provide the desired displacement.

In certain devices, the absence of such sloped surfaces can increase thevoltage necessary to displace actuatable surfaces, and can cause adecrease in actuation speed. In certain cases, the shape of the slopedsurface can also limit the amount of travel or displacement of theactuatable surface(s), further reducing the effectiveness of the device.The creation of a sloped surface in a substrate has many other usefulapplications including, for example, the formation of optical lens, aswell as other such device having a desired contour or shape.

To overcome these shortcomings, several processes have been developed toform slope etches within a substrate that are adapted to contour to thesize and shape of the actuatable surfaces. In a gray-scale lithographyprocess, for example, an optical mask and a photolithography steppersystem can be used to locally modulate the frequency of an ultraviolet(UV) light source, forming a graduated pattern of photo-resist in aphotomask layer. Once formed thereon, a dry or wet-etch step containinga single etchant solution capable of selectively etching the substratematerial is then used to transfer the graduated pattern of photo-resistto the substrate.

The resolution of many prior art methods prohibit the creation ofcertain custom sloped etches. In a gray-scale lithography process, forexample, the depth at which the slope can be formed within the substrateis often limited to only a few microns, preventing the formation of deepslopes useful in many conventional MEMS devices. Moreover, the abilityto vary the steepness of the contoured slope and or shape may be limitedby the resolution of the etching method employed, further preventing theformation of certain slopes in the substrate. As a result, there is aneed in the art for equipment and processes for creating custom slopedetches in a substrate.

SUMMARY OF THE INVENTION

The present invention pertains to equipment and processes for creating acustom sloped etch in a substrate. An illustrative process for creatinga custom sloped etch may include the steps of providing a substratehaving a surface to be etched, providing a control layer on or above thesurface of the substrate, providing at least one patterned mask layeronto or above the control layer, and then selectively etching each ofthe control layer and the substrate surface, at varying and/orcontrolled rates, to form a sloped etch in the substrate surface. Thepatterned mask layer can include one or more openings exposing thecontrol layer to etchant contained, for example, in an etch bath orother suitable etching apparatus. The geometry and/or shape of theopenings can be modified to alter the depth, steepness, shape, and othervarious characteristics of the slope, as desired.

The process of selectively etching the control layer to form the slopedetch can be accomplished by immersing the substrate in an etch bathcontaining one or more etchants adapted to selectively etch each of thesubstrate and the control layer materials. In certain embodiments, forexample, a relatively fast-rate etchant solution of nitric acid (HNO₃)can be used to selectively etch the control layer material, whereas arelatively slow-rate etchant solution of hydrofluoric acid (HF) can beused to selectively etch the substrate material. The relativeconcentrations of the two etchants can be varied throughout the etchingprocess to alter the etch rate of the substrate and/or control layer,allowing the creation of a custom sloped etch having a particular shapeor profile. In some cases, the temperature of the etch bath may also bevaried and/or controlled throughout the etching process to help alterthe etch rate of the substrate and/or control layer.

In another illustrative embodiment of the present invention, a singleetchant capable of selectively etching each of the control layer andsubstrate at different temperatures, and thus at different etch rates,can be used to form a custom sloped etch in a substrate. In certainembodiments, for example, the materials forming the substrate andcontrol layer can be selected to exhibit different etch rates at varioustemperature ranges. When placed within an etch bath including one ormore heaters, for example, the temperature of the etchant can be variedin a manner that alters the etch rate in one material (e.g. thesubstrate material) more or less relative to the other material (e.g.the control layer material). By adjusting the temperature of the etchbath during the etching process, any number of desired shapes can beformed on the substrate.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A-1D are schematic views illustrating the formation of a controllayer and a photomask on a substrate;

FIG. 2 is a diagrammatic view showing the masked substrate of FIG. 1placed within an etch bath containing multiple etchants;

FIGS. 3A-3C are schematic views illustrating the creation of a customsloped etch in the masked substrate of FIG. 1;

FIG. 4 is a graph showing an illustrative custom sloped etch formed inaccordance with the process of FIGS. 3A-3C.

FIG. 5 is a schematic view showing the masked substrate of FIG. 1 placedwithin another illustrative etching apparatus containing a singleetchant;

FIGS. 6A-6D are schematic views illustrating the creation of a customsloped etch using a control layer and a photomask having a rectangularslot; and

FIGS. 7A-7D are schematic views illustrating the creation of a customsloped etch using a control layer and a photomask having multipleopenings.

DETAILED DESCRIPTION OF THE INVENTION

The following description should be read with reference to the drawings,in which like elements in different drawings are numbered in likefashion. The drawings, which are not necessarily to scale, depictselected embodiments and are not intended to limit the scope of theinvention. Although examples of construction, dimensions, and materialsare illustrated for the various elements, those skilled in the art willrecognize that many of the examples provided have suitable alternativesthat may be utilized.

Referring now to FIGS. 1A-1D, an illustrative process of forming acontrol layer and photomask on a substrate will now be described. Theprocess, represented generally by reference number 10, may begin withthe step of providing a substrate 12 having a surface 14 to be etched inaccordance with several steps discussed herein. Substrate 12 mayinclude, for example, a thin wafer of quartz sometimes used in theconstruction of a MEMS electrostatic actuator, optical lens, or othersuch device having a desired contour or shape. In certain embodiments,for example, substrate 12 may be provided as part of the bottom and/ortop curved surfaces of an electrostatic actuator, as part of an opticallens, or any other suitable device. While quartz may be used for thesubstrate material in the illustrative embodiment, it should beunderstood that other materials such as silicon, gallium, arsenide,germanium, glass, etc. could also be used, if desired.

As can be further seen in FIG. 1A, a sacrificial control layer 16 can beapplied onto the surface 14 of the substrate 12. The control layer 16can be formed on the substrate 12 using any number of suitabledeposition techniques known in the art. In certain embodiments, forexample, the control layer 16 can be formed by sputtering metallic (e.g.Nickel) particles onto the surface 14 using a suitable sputteringprocess such as laser sputtering. Other methods such as vapor depositionor adhesion could also be utilized, if desired. In some embodiments, thecontrol layer 16 may include more than one layer, with at least some ofthe layers exhibiting different etch characteristics.

The control layer 16 should typically include a material different fromthat used in forming the substrate 12. In certain embodiments, forexample, the control layer 16 can include a layer of nickel having athickness of approximately 1 to 2 μm. Other materials and/or dimensionsare also possible, however, depending on the particular slopecharacteristic desired in the surface 14. As is discussed in furthersteps below, the various properties of the materials used in forming thesubstrate 12 and control layer 16 can be used to control the etch ratewithin the surface 14 of the substrate 12, allowing a custom sloped etchto be formed in the substrate 12.

FIG. 1B is a schematic view showing the formation of a patternedphotomask 18 onto the control layer 16 of FIG. 1A. As shown in FIG. 1B,the photomask 18 can include a first photomask layer 20 disposed overthe control layer 16, and a second (optional) photomask layer 22disposed over the first photomask layer 20. In certain embodiments, thefirst photomask layer 20 can include a relatively thin (e.g. 5 Å thick)layer of silicon nitride (SiN) film or other suitable material that actsas a mask to prevent the flow of etchant into the control layer 16. Tofacilitate adhesion of the SiN film in those embodiments wherein thecontrol layer 16 is formed of nickel, a thin layer of chrome may be usedas an intermediate layer to bond the two layers 16,20 together.

In certain embodiments, it may be desirable to bimorph the photomask 18to cause it to curl and/or displace in a direction away from the surface14 of the substrate 12 during the etching process. The second photomasklayer 22 can include a material similar to that of the first photomasklayer 20, or can include a material having different mechanical and/orthermal properties than that of the first photomask layer 20. In certainembodiments, for example, the second photomask layer 22 can include arelatively thin (e.g. 5 Å thick) layer of polysilicon applied over thefirst photomask layer 20 at room temperature. To bimorph the photomask18, the first photomask layer 20 can be applied to the control layerunder compression whereas the second photomask layer 22 can be appliedunder tension, imparting a residual stress within the photomask 18 thatcauses it to curl and/or displace in a particular manner as the controllayer 16 is being removed.

While the application of a second photomask layer 22 is specificallyillustrated in FIG. 1B, it should be understood that other methods maybe employed to bimorph the photomask 18, if desired. In one alternativemethod, for example, a single photomask layer having a coefficient ofthermal expansion different than that of the material forming thecontrol layer 16 could be used to bimorph the photomask 18. In use, thedifference in thermal coefficients causes the photomask 18 to thermallyexpand at a greater or lesser rate than the control layer 16, impartinga bias to the two materials that causes the photomask 18 to curl and/ordisplace during etching.

FIG. 1C is a schematic view showing the formation of an opening 24through the photomask layers 20,22 to expose at least a portion of theunderlying control layer 16. Formation of the opening 24 can beaccomplished using any suitable technique such as photolithography.

FIG. 1D is a top view of the substrate 12 of FIG. 1C, showing the shapeof the opening 24 in greater detail. As can be seen in FIG. 1D, theopening 24 may define a longitudinal slit 32 having a width W and alength L. In other embodiments, however, the dimensions of the opening24 can be arranged to form some other desired arrangement.

FIG. 2 is a diagrammatic view showing the masked substrate 12 of FIG. 1placed within an etching apparatus 38 containing multiple etchantsolutions. Etching apparatus 38 includes an etch bath 40 containing oneor more heater elements 42 and one or more temperature sensors 44electrically connected to a controller 46 that can be used to monitorand/or regulate the temperature of fluid within the etch bath 40. Anoptional overflow tube 48 can also be provided to maintain the fluidlevel within the etch bath 40 at a particular level, if desired.

As can be further seen in FIG. 2, a number of pipes 50,52 can be used todeliver a number of etchants into the etch bath 40. A first etchant 54adapted to selectively etch the control layer 16 can be deliveredthrough pipe 50 and into the etch bath 40. In certain embodiments, forexample, the first etchant 54 can include a fast-rate etchant solutionof nitric acid (HNO₃) that can be used to etch the nickel forming thecontrol layer 16 in some embodiments. The flow of first etchant 54 canbe varied using a flow control valve 42 or other suitable flow controlmeans.

A second etchant 58 adapted to selectively etch the substrate 12 canalso be delivered into the etch bath 40 via a second pipe 52. Incontrast to the first etchant 54, the second etchant 58 may be arelatively slow rate-etchant configured to etch the substrate 12 at aslower rate than the first etchant 54. In certain embodiments, forexample, a diluted solution of hydrofluoric acid (HF) can be utilized toetch the substrate 12 at a rate of approximately 1 to 400 times slowerthan the etch rate of the first etchant 54. A flow control valve 60 orother suitable flow control means can be used to adjust the flow ofsecond etchant 58 into the etch bath 40.

FIGS. 3A-3C are schematic views illustrating the creation of a customsloped etch in the substrate 12 of FIG. 1. At a first time t₁ depictedin FIG. 3A, substrate 12 is shown immediately after the initiation ofthe etching process, wherein the substrate 12 is immersed in an etchingapparatus containing one or more etchants configured to selectively etcheach of the substrate 12 and the control layer 16. In certainembodiments, for example, FIG. 3A may depict an initial view of thesubstrate 12 after being immersed within the etching apparatus 38 ofFIG. 2. It should be understood, however, that the various illustrativeetching stages depicted in FIGS. 3A-3C can be accomplished using othermethods and/or techniques described herein, including the use of asingle etchant solution as discussed herein with respect to FIG. 5.

Based on the relatively weak concentration of the second etchant 58(e.g. hydrofluoric acid (HF)) contained within the etch bath 40, theetch rate within the control layer 16 is greater than the etch ratewithin the substrate 12. In certain embodiments, for example, therelatively fast-rate first etchant 54 can be configured to etch thecontrol layer 16 at a rate of about 1 to 10 microns/min, whereas therelatively slow-rate second etchant 58 can be configured to etch thesubstrate 12 at a rate of about 0.01 to 1.0 microns/min. As shown inFIG. 3A, this initial combination of first etchant 54 and second etchant58 results in the formation of a gap 62.

FIG. 3B is a schematic view showing the etching of substrate 12 andcontrol layer 16 at a second time t₂. As can be seen in FIG. 3B, therelative concentrations of the first and second etchants 54,58 causesthe gap 62 to significantly widen between times t₁ and t₂, forming acurved surface 64 within the surface 14 of the substrate 12. In contrastto the lateral etch rate, which remains substantially constant duringthe etching process, the vertical etch rate will vary based on factorssuch as the size and geometry of the mask opening 24, the concentrationand temperature of etchant(s) within the etch bath, and the materialcharacteristics of the substrate 12 and control layer 16.

FIG. 3C is a schematic view showing the substrate 12 at a third time t₃at or near the conclusion of the etching process. As shown in FIG. 3C,the relative concentrations of the etchant(s) within the etch bath haveincreased the width and, to a lesser degree, the depth D of the gap 62.In certain embodiments, the etching process can be continued for aduration sufficient to etch away all or a portion of the control layer16. The duration necessary to accomplish this will depend in part on thematerial of the substrate 12 and control layer 16, the concentrations ofthe etchant(s) used, and the dimensions of the substrate 12.

The amount of etching occurring within the substrate 12 can also be madeto depend on the characteristics of the photomask 18 used. When bimorphproperties are imparted to the photomask layers 20,22, for example, thephotomask 18 can be configured to curl upwardly away from the surface 14of the substrate 12, allowing more etchant to become entrained withinthe gap 62. The existence of more etchant within the gap 64 tends toaccelerate the vertical etch rate of the substrate 12 during the etch,in some cases forming a slope having a greater depth D.

As can be further seen in FIG. 3C, the slope of the curve 64 can bevaried during the etching process to form a contour within the surface14 of the substrate 12. In the illustrative slope depicted in FIG. 3C,for example, the relative concentrations of the etchant(s) used duringthe etching process can be adjusted to create a number of inflectionpoints 66 within the curved surface 64, forming an S-shaped slope. Thelocation of the inflection points 66 and the steepness of the curvedsurface 64 can be varied to alter the shape of the slope, as desired.The depth D of the slope can also be varied, as desired, to produce aparticular profile or shape. In certain embodiments, for example, adepth D of about 4 to 8 μm may be achieved into the surface 14 of thesubstrate 12 using the methods discussed herein. However, other depthscan also be achieved, as desired. Once the desired shape has been formedwithin the surface 14 of the substrate 12, the photomask 18 andremaining control layer 16 (if any) can then removed, leaving intact thecustom sloped etch formed in the substrate 12.

FIG. 4 is a graph showing an illustrative custom sloped etch 68 formedin accordance with the illustrative process of FIGS. 3A-3C. As shown inFIG. 4, the relative concentration of the first etchant 54 issignificant in comparison to the concentration of the second etchant 58,causing a greater amount of lateral etching than vertical etching.

A first curved region 70 can be formed in the substrate 12 between timest₁ and t₂ The first curved region 70 can be formed by varying relativeconcentrations and/or temperature of first and second etchants 54,58contained within the etch bath 40. In certain embodiments, for example,the first curved region 68 can be formed by adding an initial amount ofHNO₃ and HF within the etch bath 40 (at time t=0), and then steadilyincreasing the amount of HF between times t₁ and t₂ to graduallyincrease the vertical etch rate within the substrate 12.

A second curved region 72 can also be formed in the substrate 12 betweentimes t₂ and t₃. In contrast to the first curved region 70, the secondcurved region 72 can be formed, for example, by shutting-off the flow ofHF into the etch bath 40 and gradually increasing the amount of HNO₃contained within the etch bath to gradually decrease the vertical etchrate within the substrate 12. As can be seen at time t₂ in FIG. 4, forexample, an inflection 66 (FIG. 3C) is created at time t₂ when the flowrates of the first and second etchants 54,58 are adjusted to graduallydecrease the vertical etch during this time. By adjusting the relativeconcentrations of the first and second etchant solutions 54,58 in thismanner, the steepness of the formed slope etch 68 can be made gradual,in some cases on the order of only a few degrees.

The characteristics of the sloped etch 68 can further be altered by theselection of etchants used. In certain embodiments, for example, ananisotropic etchant exhibiting crystallinity dependence can be utilizedto produce other desired profiles in a crystalline substrate such assilicon, if desired. Other factors such as the concentration of theetchant can also be exploited to create a desired slope in thesubstrate.

FIG. 5 is a schematic view showing the masked substrate of FIG. 1 placedwithin another illustrative etching apparatus 74 containing a singleetchant. As shown in FIG. 5, etching apparatus 74 includes an etch bath74 having one or more heater elements 78 and one or more temperaturesensors 80 electrically connected to a controller 82 that can be used toregulate and/or monitor the temperature at selective times during theetching process. A single etchant 84 capable of etching both thesubstrate 12 and control layer 16 can be delivered through a pipe 86 andinto the etch bath 76. In certain embodiments, a flow control valve 90can be further provided to control the flow of etchant 84 into the etchbath 76. An optional overflow tube 88 can also be utilized to maintainthe fluid level within the etch bath 76 at a particular level, ifdesired.

To create a custom sloped etch in the substrate 12, the temperaturewithin the etch bath 76 can be varied at one or more times during theetching process to alter the respective etch rates of the substrate 12and control layer 16. The steepness of the slope imparted to thesubstrate 12 will depend on the relative etch rates of the substrate 12and control layer 16 at various temperatures. In certain embodiments,for example, the etch rate of the control layer 16 can be configured toincrease at a greater rate at a particular temperature or temperaturerange (e.g. at 100° C.). In general, the greater the difference inrelative etch rates between the two materials, the more gradual theslope that can be imparted to the substrate 12, all other factors beingthe same. Thus, by selectively increasing and/or decreasing thetemperature within the etch bath 76, a desired sloped etch can be formedin the substrate 12.

FIGS. 6A-6D are schematic views illustrating the creation of a customsloped etch using a control layer and a patterned photomask having arectangular slot. The process, represented generally by reference number92, is similar to that described above with respect to FIGS. 3A-3C,beginning with the step of providing a substrate 94 having a surface 96to be etched. Substrate 94 may include, for example, a thin wafer ofquartz used in the construction of a MEMS electrostatic actuator,optical lens, or other similar device having a desired contour or shape.A control layer 98 and photomask 100 can also be applied to the surface96 of the substrate 94 in a manner similar to that described above inFIGS. 1A-1C. In certain embodiments, for example, control layer 98 caninclude a layer of nickel or other suitable material applied to thesurface of a quartz substrate 94.

In the illustrative embodiment of FIGS. 6A-6D, the photomask 100includes a single layer 102 of silicon nitride (SiN) film or othersuitable mask material. As with other embodiments discussed herein, thesingle photomask layer 102 can be configured to bimorph, causing thelayer 102 to curl upwardly away from the surface 96 of the substrate 94during the etching process. In certain embodiments, for example, thephotomask layer 102 can be configured to bimorph by applying astretching (i.e. tensile) force to the photomask layer 102 while it isbeing applied to the control layer 98. Alternatively, the photomasklayer 102 can include a material having a different coefficient ofthermal expansion than that of the material forming the control layer98, causing the photomask layer 102 to shrink at a greater or lesserrate than the control layer 98.

In a first step depicted in FIG. 6A, an opening 104 can be formedthrough the single photomask layer 102 to expose at least a part of theunderlying control layer 98. FIG. 6B is a top view of the substrate 94,showing the shape of the opening 104 in greater detail. As can be seenin FIG. 6B, the opening 104 may define a rectangular slot 107 having awidth W and a length L. Similar to the longitudinal slit 32 discussedabove with respect to FIG. 1D, the rectangular slot 107 can beconfigured to form a contoured slope or profile along the length of thesubstrate 94. The width W of the rectangular slot 106, however, can bemade greater than the width W of the longitudinal slit 32 to expose moreof the underlying control layer 98.

FIGS. 6C-6D illustrate the steps of creating a custom sloped etch withinthe surface 96 of the substrate 94. As shown in a first position in FIG.6C, the existence of the rectangular slot 107 forms a channel 112 havinga substantially flat region 114. The dimensions of the flat region 114will typically depend in part on the width W and length L of therectangular slot 107.

FIG. 6D is a schematic view showing the substrate 94 at a second time ator near the conclusion of the etching process. As can be seen in FIG.6D, one or more curved surfaces 116 can also be formed within thesurface 96 of the substrate 94. The curved surfaces 116 can be formed byselectively etching each of the substrate 94 and the control layer 98using multiple etchants having differing relative etch rates. Thetemperature of the etch bath may also be controlled during the etchingprocess to help increase and/or decrease the etch rate of the substrate94 and/or control layer 98.

Alternatively, the curved surfaces 116 can be formed using singleetchant by adjusting the temperature within the etch bath at varioustimes during the etching process to increase and/or decrease the etchrate of the substrate 94 and/or control layer 98. In either case, thephotomask layer 120 can be configured to bimorph away from the surface96 of the substrate 94 during the etching process, if desired.

FIGS. 7A-7D are schematic views illustrating the creation of a customsloped etch using a control layer and a patterned photomask havingmultiple openings. The process, represented generally by referencenumber 118, can begin with the step of providing a substrate 120 havinga surface 122 to be etched. Substrate 120 may include, for example, athin wafer of quartz or other suitable material. A control layer 124 andphotomask 126 can also be applied to the substrate 120 in a mannersimilar to that described above with respect to FIGS. 1A-1C. In certainembodiments, for example, the control layer 124 can include a layer ofnickel or other suitable material applied to the surface of a quartzsubstrate 120.

In the illustrative embodiment of FIGS. 7A-7D, the photomask 126includes a single, thin layer 128 of silicon nitride (SiN) film or othersuitable mask material. As with other embodiments discussed herein, thesingle photomask layer 128 can be configured to bimorph during etching,causing the layer 128 to curl upwardly away from the surface 122 of thesubstrate 120. The photomask 126 may define a plurality of openings130,132 that expose the control layer 124 to etchant contained, forexample, in an etch bath. As can be seen in greater detail in FIG. 7B,the openings 130,132 can each define a longitudinal slit 134,136 spacedapart from each other a distance D on the photomask layer 128.

FIGS. 7C-7D illustrate the steps of creating a custom sloped etch withinthe surface 122 of the substrate 120. In a first position illustrated inFIG. 7C, the existence of the openings 130,132 through the photomask 126initially creates a number of gaps 138,140 within the control layer 124and substrate 120. As can be seen at a later time in FIG. 7D, theexistence of multiple openings 130,132 within the photomask 126 createsa curved surface 142 having a kink 144. The distance D between thelongitudinal slits 134,136 can be varied to alter the characteristics ofthe kink 144 formed. In certain embodiments, for example, the distance Dbetween each of the longitudinal slits 134,136 can be made greater toincrease the height of the kink 252. Alternatively, the distance Dbetween each of the longitudinal slits 132,134 can be made smaller todecrease the height of the kink 252. Other factors such as thedimensions of the longitudinal slits 132,134 can also be adjusted toproduce a desired contour in the substrate 120. While the use of twoopenings 130,132 is specifically illustrated FIGS. 7A-7D, it should beunderstood that any number of openings could be employed to alter theshape of the slope, as desired.

Having thus described the several embodiments of the present invention,those of skill in the art will readily appreciate that other embodimentsmay be made and used which fall within the scope of the claims attachedhereto. Numerous advantages of the invention covered by this documenthave been set forth in the foregoing description. It will be understoodthat this disclosure is, in many respects, only illustrative. Changesmay be made in details, particularly in matters of shape, size andarrangement of parts without exceeding the scope of the invention.

1. A method for creating a custom sloped etch in a substrate, comprising the steps of: providing a substrate having a surface; providing a control layer above the surface of the substrate, providing a photomask above the control layer, said photomask defining at least one opening exposing at least a portion of the control layer; and selectively etching the control layer and substrate surface to form a sloped etch within the substrate surface.
 2. The method of claim 1, wherein said step of selectively etching the control layer and substrate surface comprises the steps of: applying a first etchant configured to selectively etch the control layer; and applying a second etchant configured to selectively etch the substrate.
 3. The method of claim 2, wherein the etch rate of the first etchant is greater than the etch rate of the second etchant.
 4. The method of claim 2, further comprising the step of adjusting the relative concentrations of the first and second etchants during said step of selectively etching the control layer and substrate surface.
 5. The method of claim 2, wherein said first etchant is a fast-rate etchant solution of nitric acid.
 6. The method of claim 2, wherein said second etchant is a slow-rate etchant solution of hydrofluoric acid.
 7. The method of claim 1, wherein said step of selectively etching the control layer and substrate surface comprises the steps of: placing the substrate within an etch bath containing at least one etchant solution; and heating the substrate at one or more intervals to selectively adjust the relative etch rates of the substrate and the control layer.
 8. The method of claim 1, wherein said substrate includes quartz.
 9. The method of claim 1, wherein said control layer includes nickel.
 10. The method of claim 1, wherein said step of forming a photomask above the control layer comprises the steps of: providing a first photomask layer above the substrate; and providing a second photomask layer on the first photomask layer.
 11. The method of claim 10, wherein said first photomask layer includes a compressive layer of silicon nitride.
 12. The method of claim 10, wherein said second photomask layer includes a tensile layer of polysilicon.
 13. The method of claim 1, wherein said photomask is a bimorph photomask.
 14. The method of claim 1, wherein said at least one opening comprises a longitudinal slit.
 15. The method of claim 1, wherein said at least one opening comprises a rectangular slot.
 16. The method of claim 1, wherein said at least one opening comprises a plurality of openings.
 17. The method of claim 1, wherein said sloped etch is an S-shaped sloped etch.
 18. The method of claim 1, wherein said sloped etch has a depth of between about 4 to 8 μm.
 19. The method of claim 1, further comprising the step of removing the control layer and photomask after said step of selectively etching the control layer and substrate surface.
 20. A method for creating a custom sloped etch in a substrate, comprising the steps of: providing a substrate having a surface; providing a control layer above the surface of the substrate, providing a photomask above the control layer, said photomask defining at least one opening exposing at least a portion of the control layer; applying a first etchant configured to selectively etch the control layer; applying a second etchant configured to selectively etch the substrate; and adjusting the relative concentrations of the first and second etchants to form a sloped etch within the substrate surface.
 21. The method of claim 20, wherein the etch rate of the first etchant is greater than the etch rate of the second etchant.
 22. The method of claim 20, wherein said first etchant is a fast-rate etchant solution of nitric acid.
 23. The method of claim 20, wherein said second etchant is a slow-rate etchant solution of hydrofluoric acid.
 24. The method of claim 20, wherein said substrate includes quartz.
 25. The method of claim 20, wherein said control layer includes nickel.
 26. The method of claim 20, wherein said step of applying a photomask above the control layer comprises the steps of: providing a first photomask layer above the substrate; and providing a second photomask layer on the first photomask layer.
 27. The method of claim 26, wherein said first photomask layer includes a compressive layer of silicon nitride.
 28. The method of claim 26, wherein said second photomask layer includes a tensile layer of polysilicon.
 29. The method of claim 20, wherein said photomask is a bimorph photomask.
 30. The method of claim 20, wherein said at least one opening comprises a longitudinal slit.
 31. The method of claim 20, wherein said at least one opening comprises a rectangular slot.
 32. The method of claim 20, wherein said at least one opening comprises a plurality of openings.
 33. The method of claim 20, wherein said sloped etch is an S-shaped sloped etch.
 34. The method of claim 20, wherein said sloped etch has a depth of between about 4 to 8 μm.
 35. The method of claim 20, further comprising the step of removing the control layer and photomask after said step of selectively etching the control layer and substrate surface.
 36. A method for creating a custom sloped etch in a substrate, comprising the steps of: providing a substrate having a surface; providing a nickel control layer above the surface of the substrate, providing a photomask above the control layer, said photomask defining at least one opening exposing at least a portion of the control layer; applying a fast-rate etchant solution of nitric acid configured to selectively etch the control layer; applying a slow-rate etchant solution of hydrofluoric acid configured to selectively etch the substrate; and adjusting the relative concentrations of the first and second etchant solutions to form a sloped etch in the substrate surface.
 37. A method for creating a custom sloped etch in a substrate, comprising the steps of: providing a substrate having a surface; providing a control layer above the surface of the substrate, providing a bimorph photomask above the control layer, said photomask defining at least one opening exposing at least a portion of the control layer; and selectively etching the control layer and substrate surface to form a sloped etch in the substrate surface.
 38. A system for etching a custom sloped etch in a substrate, the system comprising: a substrate having a sacrificial control layer and at least one mask layer, said at least one mask layer defining one or more openings exposing the control layer; and etching means for selectively etching the substrate and control layer to form a sloped etch in the substrate.
 39. The system of claim 38, wherein said etching means includes a first etchant source configured to adjustably etch the control layer at a first etch rate, and a second etchant source configured to adjustably etch the substrate at a second etch rate.
 41. The system of claim 40, wherein said first etch rate is greater than said second etch rate.
 42. The system of claim 39, wherein said etching means includes an etch bath and at least one heater element.
 43. The system of claim 42, further comprising a controller adapted to regulate the temperature of said at least one heater element.
 44. The system of claim 42, further comprising a temperature sensor operatively coupled to said controller, said temperature sensor being adapted to monitor the temperature within said etch bath.
 45. A system for etching a custom sloped etch in a substrate, the system comprising: a substrate having a sacrificial control layer and at least one mask layer, said at least one mask layer defining one or more openings exposing the control layer; and an etching apparatus configured to deliver at least one etchant solution into an etch bath containing the substrate, said at least one etchant solution being configured to selectively etch the substrate and control layer at an adjustable rate to form a sloped etch in the substrate.
 46. A system for etching a custom sloped etch in a substrate, the system comprising: a substrate having a sacrificial control layer and at least one mask layer, said at least one mask layer defining one or more openings exposing the control layer; and an etching apparatus configured to deliver a first etchant solution configured to adjustably etch the control layer at a first etch rate, and a second etchant solution configured to adjustably etch the substrate at a second etch rate different than said first etch rate. 